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New Cartridge Big Hum no Music

N

Nolan Olson

New Member
I have an Bang & Olufsen RX TT and it had an MC 5 cartridge. It played vinyl but volume was soft but could be heard through the speakers.
Sent cartridge off to be retipped to a nude MC 3.
Installed and all I get is a hum which increases with volume. The ground is tight and the RX phono cables are the installed ungrounded type.
Everything is as it was when it worked. Contacted vendor and he show me photos of my cartridge and the signal track readings. I tested the arm at a 20 setting on my multimeter and got a reading of 490 ohms. I tested the cartridge and got a 1 at the 20 setting but got an 890 ohms at the 2000 setting. Can the difference in resistance cause a hum? Is there a way I can test my phono pre amp socket on my receiver buy using the multimeter and a tip and ring ? Or how do I eliminate the other factors. I tried the 2 rca jacks in the phono sockets and immediately get a hum before even touching them (But they were grounded rca cords). No hum in phono mode when sockets are unused. The vendor will retest the cartridge if I sent it back, though he’s sure it’s not at fault. My receiver is an MCS 3248. If I buy a cheap pre amp to test I cannot use the phono sockets and the few others are in use. If I unplugged the cd and it worked I’d still have to buy a new receiver to make everything work because I’d be out of sockets, so I need to absolutely rule in or out the preamp and any other factors before I make a decision.
Thanks
Nolan
 
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Can we assume that you have a ground wire coming from your turntable and that it is connected to the ground lug near the phono inputs on the back of your receiver?

Are you sure that each of the headshell wires are connected to the correct pin on the back of the cartridge, and that each of those connections is good?

Did a different cartridge perform well on this turntable sometime before this one? If not, it could be a poor connection somewhere in the audio wiring inside of the turntable--between where the cartridge attaches and where the output cables attach. You should also try different cables between the turntable and the receiver at some point in this process.
 
Thanks, yes the TT is grounded tightly to the ground nut, but same as before. I cannot try new rca cables as the RX has the cables directly wired to the unit.
Looking for a multimeter test for the pre amp from the phono sockets... must be someway to test this?
 
As an explanation, the only cartridge this unit can use is the MC series and only available from one source. It’s the same cartridge that came with the but has been upgraded and refurbished. No other cartridge is available for testing, the vendor said he would send one but he has none to send at this time.
If there is a definitive way to test phono sockets to verify pre amp status that would be perfect. If the phono amp is good I will send cartridge back for testing. If it’s bad, then a new receiver is in my future.
 
Nolan Olson said:
I have an Bang & Olufsen RX TT and it had an MC 5 cartridge. It played vinyl but volume was soft but could be heard through the speakers.
Sent cartridge off to be retipped to a nude MC 3.
Installed and all I get is a hum which increases with volume.
Click to expand...
First off I'm not sure of your cartridge make and model, but sounds like a MC cartridge and your receiver has a MM phono stage. Doing a cartridge search shows a Yamaha cartridges and it's not a P mount. Edit:
Bang & Olufsen MMC 5 is what you have I assume

MMC5 Product Specifications

Description Titanium-bonded elliptical diamond, mounted on a straight aluminium cantilever
Tracking force - grams 1.5
Diamond Stylus Elliptical
Cantilever tube Straight alum.
Effective tip mass mg 0,5
Compliance mg/mN 20
Frequency 20-20000 Hz=/-dB 3
Channel separation 1000>dB 20
Output mV/cm/s RMS 0.6
Cartridge weight gram 1,6

This cartridge is a Low Output Moving Coil, your receivers phono stage is a MM cartridge design. Your hearing hum because all phono stages hum more than other inputs, and your trying to turn the volume way up because the cartridge signal is to week.
Nolan Olson said:
Everything is as it was when it worked
Click to expand...
Turntable ground wires are only used if needed, if the hum is worse using it disconnect and move it away from other wires. I personally think you have more than one issue going on.

Nolan Olson said:
Contacted vendor and he show me photos of my cartridge and the signal track readings.
Click to expand...
Is this a eBay seller that advertises retipping? If so I probably know who, and they are in no way a professional.
 
4-2-7 said:
First off I'm not sure of your cartridge make and model, but sounds like a MC cartridge and your receiver has a MM phono stage. Doing a cartridge search shows a Yamaha cartridges and it's not a P mount. Edit:
Bang & Olufsen MMC 5 is what you have I assume
Click to expand...
It would seem that something labeled "MMC 5" could be a MC cartridge. That's just B&O being B&O. Always with the clever model designations. It's a MM cartridge.
The MMC 1 through 5 series of cartridges have a unique mount applicable only to the RX and TX turntables (maybe others). Used together they track flawlessly. More resistant to outside physical influence than just about anything else out there.
The limitation is that no other cartridge can be used with that turntable. Short of trying verifying continuity of each connection you'll have to acquire a second MMC another. The MMC5 is the lowest of the model line. All are next to impossible to find.
Soundsmith currently makes new replacement B&O cartridges. Some real technically impress ones.
https://www.sound-smith.com/bo-replacement-cartridge-models
 
ctjetta said:
It would seem that something labeled "MMC 5" could be a MC cartridge. That's just B&O being B&O. Always with the clever model designations. It's a MM cartridge.
The MMC 1 through 5 series of cartridges have a unique mount applicable only to the RX and TX turntables (maybe others). Used together they track flawlessly. More resistant to outside physical influence than just about anything else out there.
The limitation is that no other cartridge can be used with that turntable. Short of trying verifying continuity of each connection you'll have to acquire a second MMC another. The MMC5 is the lowest of the model line. All are next to impossible to find.
Soundsmith currently makes new replacement B&O cartridges. Some real technically impress ones.
https://www.sound-smith.com/bo-replacement-cartridge-models
Click to expand...
Sound-smith is where it was retipped, they will take it back and retest but I want to be sure my phono stage is working... there must be some way using a multimeter to test the phono sockets when powered on to determine if phono amp is working? I have continuity on all TT arm sockets at 490 ohms and the cartridge pins were 890 ohms.
 
you can test with a very low signal input from an ipod or similar .it wont sound its best but shouldn't cause a hum .
 
Why would a retip cause a ground hum? Was the receiver or table moved to remove cartridge? Maybe somehow the ground got disconnected inside the table. Or, maybe moving it caused a break in the wire. Might still be connected to thelug, but maybe it is broken somewhere along its length.
 
Todd MacDona said:
Why would a retip cause a ground hum? Was the receiver or table moved to remove cartridge? Maybe somehow the ground got disconnected inside the table. Or, maybe moving it caused a break in the wire. Might still be connected to thelug, but maybe it is broken somewhere along its length.
Click to expand...
Worth checking out. Thanks, the TT wasn’t moved
But perhaps the ground is at fault somewhere.
 
Didn’t find a ground problem at TT unless receiver ground screw is bad. I’m buying a vintage receiver today...an upgrade...and we’ll see if it works or cartridge is going back.
Nolan
 
Todd or whoever, I bought a different receiver and now I can barely hear the faint music but also a hum.
So I am thinking a new preamp or hum eliminator.
One is Buzz Off by Rolls for $35 the other is a 5 star phono pre amp from Pluto for $99. But can I plug either into Tape 2 Play and get sound? ( don’t think I can plug into phono jacks??) I only have one Aux and the CD uses it.
 
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